What happens to Pub/Sub messages if no subscription acknowledges them before the message retention duration expires?

Question

Google Cloud (GCP) — Hard

What happens to Pub/Sub messages if no subscription acknowledges them before the message retention duration expires?

Accepted Answer

When Pub/Sub messages exceed their retention duration without acknowledgment, they are discarded. The correct answer, permanent deletion, occurs because unacknowledged messages are removed from the topic after the specified retention period. Incorrect options, such as automatic archiving or re-publishing, do not align with Pub/Sub's message handling behavior.